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Iridium's Loss Is Astronomers' Gain

A spectacular business flop is evoking sweet sorrow among radio astronomers. The once high-flying Iridium mobile phone company last week announced that it had pulled the plug on its $5 billion satellite fleet and will eventually send the 68 orbiting craft into fiery death dives in Earth's atmosphere. That means an end to the electronic smog that clouded sensitive telescopes. "I'm not going to say Iridium deserved it, but they certainly were not good neighbors to astronomers," says Willem Baan, director of Holland's Westerbork Observatory. The experience has also steeled astronomers' resolve to prevent erosion of important frequencies.

Iridium's globe-girdling constellation was supposed to be the next big thing in mobile communications when it went live in late 1998 (Science, 2 October 1998, p. 34). But radio astronomers weren't thrilled, because the satellites produced static that interfered with the very faint cosmic signals they study. In particular, Iridium threatened a 1612-megahertz radio signal produced by hydroxyl masers, intense blasts of laserlike radio waves that have provided important insights into how stars are born and die. After 6 years of often tense negotiations, the company agreed to provide some unobstructed listening hours each day to radio telescopes in Europe, the United States, and India, and to fix the problem in newer satellites. That deal is now moot, however, as technical glitches and Iridium's high prices--the phones cost $3000 each and calls up to $7 a minute--forced the company to shut down on 17 March.

The Iridium episode has prompted astronomers "to become much more vigilant" about the interference threat from the growing communications industry, says Baan. In the United States, for instance, a recent government proposal to loosen standards on satellite radio emissions drew angry replies from 50 concerned astronomers, an unprecedented response. And researchers are organizing to protect key bandwidths at an international spectrum-allocation conference to be held in Istanbul in May.

Meanwhile, Iridium's demise will also lighten the load on some optical astronomers. The reflective solar panels on each satellite produce bright flashes that amateur sky watchers occasionally mistake for new celestial bodies, says Daniel Green of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. "At least we won't be getting these weekly reports from people saying they've discovered another naked-eye supernova," he says.